Explorer problem and KOER test

[carlosm180]

Hello from Italy!
I have a great problem with my Explorer 1991-1994: when I try to accelerate, engine stop to work (as it is a bi-fuel with LPG, it's able to run in LPG mode).
I made a KOER test and somethings are strange:
-no ID engine is shown
- first code is 998 and then it flash 157 code (I read that 998 is the last code!)
-no cylinder balance test is done.... but perhaps I make a mystake in cylinder balance testing procedure....
Any suggestion? MAF?
4X4Thanks
Carlo

 

[MrShorty]

Do you get a corresponding MAF code from the KOEO test? It certainly looks like something is wrong with the MAF circuit, in addition to checking the results from the KOEO test, I'd probably start with a thorough inspection of the MAF and wiring.

 

[carlosm180]

Do you get a corresponding MAF code from the KOEO test? It certainly looks like something is wrong with the MAF circuit, in addition to checking the results from the KOEO test, I'd probably start with a thorough inspection of the MAF and wiring.

I have disconnected battery for a night, then i started KOEO test; the codes are:
111
-pause/reading memory code-> 157 and then 543(an error about fuel pump, but it appears a "random code", because in my first koeo test it didn't appear!).

 

[MrShorty]

I know this problem has come up before. It seems like every other time it has come up, it has been a bad MAF, or something else in the MAF circuit.

I had a similar intermittent CM 542/543. Couldn't figure out what it was until one morning it wouldn't start, and then I found a loose connection between the fuel pump fuse and the fuel pump relay. Of course, a loose connection anywhere else in the fuel pump circuit could trigger the same CM code, and you probably won't be able to find it until one morning when it won't start or something like that. I might suggest wiggling some of the connectors/wires in the fuel pump circuit in hopes of finding the bad connection before it leaves you stranded, but you still might not find it.

 

[carlosm180]

I test MAF voltage (both MAF sensor and MAF connector) and all work fine (except for min MAF voltage that is 0.27V against 0.3v).
Howether, there is 157 and 998 code still (but now koer shows 157 code before 998 ) and I'm not be able to run cylinder balance test...

 

[wishiwerefishn]

code 998 is a failure code it means the ecm is running the engine under a minamal operations failure program but don't worry this is what it's suposed to do when the ecm gets a fault code from a major sensore like a maf or o2 sensor. if it shows a 157 then its your maf. cleaning it may only reduce the symtoms not stop them and they will come back. replace the maf to solve it completely then wipe the codes and run them again you sould get a 111 code which mean everything is ok now. however when you get a maf code after fixing it you will somtimes get a 137 this is your o2 sensores check how many you have before heading to the parts store if this comes up if not good luck.